In order to strike a balance it is important to know one's audience. If one can know and partly understand his or her audience, they will be able to focus on certain feelings and balance the amount of feeling based speech compared to the logic based part of a speech. Just as the book says, the information you share "depends on the disposition and attitudes of the audience" (pg.71). While both feelings and logic are super important, one should not out weigh the other by more than a little bit. It is important to reach the feelings of the audience but also share good truth and logic.
It can be difficult to see the audience's disposition but it can be key to captivating your audience.
I like your tactic of reading the audience's reaction to a speech. Understanding their disposition will help the speaker determine whether or not they have gone too far on either extreme.
This is really well worded. The quote added credibility and it was easy to read.